Graphene macro-assembly-fullerene composite for electrical energy storage

ABSTRACT

Disclosed here is a method for producing a graphene macro-assembly (GMA)-fullerene composite, comprising providing a GMA comprising a three-dimensional network of graphene sheets crosslinked by covalent carbon bonds, and incorporating at least 20 wt. % of at least one fullerene compound into the GMA based on the initial weight of the GMA to obtain a GMA-fullerene composite. Also described are a GMA-fullerene composite produced, an electrode comprising the GMA-fullerene composite, and a supercapacitor comprising the electrode and optionally an organic or ionic liquid electrolyte in contact with the electrode.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 15/260,197, filed Sep. 8, 2016, which is hereby incorporated byreference in its entirety.

FEDERAL FUNDING STATEMENT

The United States Government has rights in the invention pursuant toContract No. DE-AC52-07NA27344 between the U.S. Department of Energy andLawrence Livermore National Security, LLC, for the operation of LawrenceLivermore National Laboratory.

BACKGROUND

Supercapacitors (also known as ultracapacitors or electricaldouble-layer capacitors) have the potential to replace Li ion batteriesas the next-generation electrical energy storage technology in demandingapplications due to their high power density and excellent cyclingstability. Graphene-based supercapacitor electrodes are particularlypromising because they feature high surface area, good electricalconductivity, and chemical inertness. Researchers at Lawrence LivermoreNational Laboratory have developed binder-free 3D mesoporous graphenemacro-assemblies (GMAs) that have exceptionally high surface area (˜1500m²/g) and excellent conductivity (˜100 S/m) using abundant and low coststarting materials. These GMAs offer many advantages over traditionalcarbon-based supercapacitor electrodes such as deterministic controlover pore morphology, increased conductivity, and the absence ofconductive filler and binder materials. However, the interfacialcapacitance of graphene-based electrodes is limited by the low densityof states at the Fermi level to ˜10 mF/cm² (corresponding to 0.01electron per carbon atom for the stability window of aqueouselectrolytes). To replace Li-ion batteries in energy-demandingapplications, these materials need improvements to their energy storageperformance.

Fullerenes (also known as Bucky-balls) can store 10 times the energy percarbon as graphene (6 electrons per C₆₀ molecule or 1 electron per 10carbon atoms). Since the discovery of C₆₀, fullerenes have attractedpronounced attention due to their applications in medicinal chemistry(as MM contrast agents, in tumor diagnosis and radio-immunotherapy),material science and photovoltaic solar cells, among others.Functionalization or chemical modification of fullerenes has be used toincrease their solubility, allow their characterization and exploretheir physical and chemical properties. Fullerenes possess highlyreactive double bonds that allow the study of their reactivity usingdifferent types of reactions, such as oxidation reactions, transitionmetal complexation, hydrogenations, halogenations, radical additions,cycloadditions (1,3-dipolar, [2+2], [4+2], [3+2], [2+2+1]), addition ofnucleophiles (Bingel additions), silylations and electrosynthesis.

SUMMARY

One aspect the invention described herein relates to a method forproducing a GMA-fullerene composite, comprising providing a GMAcomprising a three-dimensional network of graphene sheets crosslinked bycovalent carbon bonds, and incorporating at least 20 wt. % of at leastone fullerene compound into the GMA based on the initial weight of theGMA to obtain the GMA-fullerene composite.

In some embodiments, the fullerene compound is covalently bound to thegraphene sheets. In some embodiments, the incorporating step comprisesreacting the GMA with least one diazonium functionlized fullerene.

In some embodiments, the diazonium functionlized fullerene isrepresented by F*—(R)_(n), wherein: F* comprises a fullerene having asurface comprising six-membered and five-membered rings, R comprises adiazonium group and a conjugated linker covalently connecting thediazonium group to the fullerene, and n is at least one.

In some embodiments, n is 1 or 2, F* is C₆₀ or C₇₀, and R is selectedfrom the group consisting of

In some embodiments, n is 1 or 2, F* is C₆₀ or C₇₀, and R is selectedfrom the group consisting of

In some embodiments, the fullerene compound is noncovalently attached tothe graphene sheets. In some embodiments, the incorporating stepcomprises incubating the GMA in a solution comprising at least onephenylamine functionlized fullerene.

In some embodiments, the phenylamine functionlized fullerene isrepresented by F*—(R)_(n), wherein: F* comprises a fullerene having asurface comprising six-membered and five-membered rings, R comprises aphenylamine group and a conjugated linker covalently connecting thephenylamine group to the fullerene, and n is at least one.

In some embodiments, n is 1 or 2, F* is C₆₀ or C₇₀, and R is selectedfrom the group consisting of

In some embodiments, n is 1 or 2, F* is C₆₀ or C₇₀, and R is selectedfrom the group consisting of

In some embodiments, at least 50 wt. % of the fullerene compound areincorporated into the GMA based on the initial weight of the GMA.

In some embodiments, at least 100 wt. % of the fullerene compound areincorporated into the GMA based on the initial weight of the GMA.

Another aspect of the invention relates to a GMA-fullerene compositeproduced by the method described herein.

In some embodiments, the GMA-fullerene composite is a monolith having athickness of at least 1 mm.

In some embodiments, the GMA-fullerene composite has an electricalconductivity of at least 10 S/m.

In some embodiments, the GMA-fullerene composite has a mesopore volumeof at least 0.5 cm³/g.

In some embodiments, the GMA-fullerene composite has a BET surface areaof at least 200 m²/g.

In some embodiments, the GMA-fullerene composite has a Young's modulusof at least 20 MPa.

A further aspect of the invention relates to an electrode comprising theGMA-fullerene composite described herein.

An additional aspect of the invention relates to a supercapacitorcomprising the electrode described herein.

In some embodiments, the supercapacitor further comprises an organic orionic liquid electrolyte in contact with the electrode.

These and other features, together with the organization and manner ofoperation thereof, will become apparent from the following detaileddescription when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: (A) a GMA-C₆₀ composite obtained by noncovalentlyfunctionalizing the GMA with 4.5 mM C₆₀; (B) CV of a GMA-C₆₀ with 13%loading of C₆₀ in MeCN/TBAP electrolyte (5 mV/s).

FIG. 2: (A) a GMA-PA-C₆₀ composite obtained by noncovalentlyfunctionalizing the GMA with 7 mM PA-C₆₀; (B) CV of a GMA-PA-C₆₀composite with 50% loading of PA-C₆₀ in MeCN/TBAP electrolyte (5 mV/s).

FIG. 3: CV of a non-functionalized GMA in MeCN/TBAP electrolyte (5mV/s).

FIG. 4: CV of a GMA-fullerene composite with a final loading of 138% inMeCN/TBAP electrolyte (10 mV/s). This GMA-fullerene composite wasobtained by covalently functionalizing the GMA with diazonium-C₆₀.

FIG. 5: Examples of phenylamine-functionalized fullerene compounds forfunctionalization of GMA.

FIG. 6: Additional examples of fullerene compounds for functionalizationof GMA.

FIG. 7: CV in MeCN/TBAP electrolyte of a GMA-C₆₀ with 17 wt. % loadingof C₆₀ (5 mV/s, cycle 1, black line) and non-functionalized GMA (5 mV/s,cycle 1, red line).

FIG. 8: CV in MeCN/TBAP electrolyte of a GMA-C₆₀-1 composite with 44 wt.% loading of C₆₀-1 (5 mV/s, cycle 1, black line) and non-functionalizedGMA (5 mV/s, cycle 1, red line).

FIG. 9: CV in MeCN/TBAP electrolyte of a covalently functionalizedGMA-fullerene composite with diazonium-C₆₀, final loading 138 wt. % (5mV/s, black line) and non-functionalized GMA (5 mV/s, cycle 1, redline).

FIG. 10: Examples of diazonium-functionlized fullerene compounds forfunctionalization of GMA.

DETAILED DESCRIPTION

Reference will now be made in detail to some specific embodiments of theinvention contemplated by the inventors for carrying out the invention.Certain examples of these specific embodiments are illustrated in theaccompanying drawings. While the invention is described in conjunctionwith these specific embodiments, it will be understood that it is notintended to limit the invention to the described embodiments. On thecontrary, it is intended to cover alternatives, modifications, andequivalents as may be included within the spirit and scope of theinvention as defined by the appended claims.

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention.Particular example embodiments of the present invention may beimplemented without some or all of these specific details. In otherinstances, well known process operations have not been described indetail in order not to unnecessarily obscure the present invention.

Various techniques and mechanisms of the present invention willsometimes be described in singular form for clarity. However, it shouldbe noted that some embodiments include multiple iterations of atechnique or multiple instantiations of a mechanism unless notedotherwise.

Introduction

The article, “Mechanically Robust 3D Graphene Macroassembly with HighSurface Area,” Worsley et al., Chem. Commun., 48:8428-8430 (2012), isincorporated by reference in its entirety.

The article, “Toward Macroscale, Isotropic Carbons withGraphene-Sheet-Like Electrical and Mechanical Properties,” Worsley etal., Adv. Funct. Mater., 24:4259-4264 (2014), is incorporated byreference in its entirety.

The article, “Synthesis and Characterization of Highly CrystallineGraphene Aerogels,” Worsley et al., ACS Nano, 8:11013-11022 (2014), isincorporated by reference in its entirety.

US Patent Publication No. 2012/0034442 to Worsley et al., “GrapheneAerogels,” is incorporated by reference in its entirety.

US Patent Publication No. 2014/0178289 to Worsley et al., “High-Density3D Graphene-Based Monolith and Related Materials, Methods, and Devices,”is incorporated by reference in its entirety.

U.S. patent application Ser. No. 14/820411 to Worsley et al., “HighlyCrystalline Graphene Aerogels,” is incorporated by reference in itsentirety.

Method For Making GMA-Fullerene Composite

Many embodiments of the invention described herein relates to a methodfor producing a GMA-fullerene composite, comprising providing a GMAcomprising a three-dimensional network of graphene sheets crosslinked bycovalent carbon bonds, and incorporating at least 20 wt. % of at leastone fullerene compound into the GMA based on the initial weight of theGMA to obtain the GMA-fullerene composite.

In some embodiments, the method comprises immersing GMA in a solution ofthe fullerene compound. In some embodiments, the solution comprises atleast one organic solvent. Suitable solvents include, for example, CS₂,CH₂Cl₂, CS₂:CH₂Cl₂, and THF.

In some embodiments, the concentration of the fullerene compound in thesolution is about 1-20 mM, or about 2-15 mM, or about 3-10 mM, or about4-8 mM. In some embodiments, the concentration of the fullerene compoundin the solution is about 0.5-8 mM.

In some embodiments, the method comprises heating the GMA immersed in asolution of the fullerene compound. In some embodiments, the methodcomprises heating the GMA immersed in a solution of the fullerenecompound at a temperature of 50-100° C. In some embodiments, the methodcomprises heating the GMA immersed in a solution of the fullerenecompound for 12 to 96 hours.

In some embodiments, the method comprises in-situ synthesis of diazoniumfunctionlized fullerene and covalent bonding thereof to GMA.

In some embodiments, the fullerene compound is covalently bound to thegraphene sheets. In some embodiments, the method comprises reacting theGMA with least one fullerene compound represented by F*—(R¹)_(n),wherein: F* comprises a fullerene having a surface comprisingsix-membered and five-membered rings, R¹ comprises a reactive group(e.g., diazonium) and a conjugated linker covalently connecting thereactive group to the fullerene, and n is at least one.

In some embodiments, the method comprises reacting the GMA with leastone diazonium functionlized fullerene. In some embodiments, thediazonium functionlized fullerene is represented by

F*—(R¹)_(n), wherein: F* comprises a fullerene having a surfacecomprising six-membered and five-membered rings, R¹ comprises adiazonium group and a conjugated linker covalently connecting thediazonium group to the fullerene, and n is at least one.

In one embodiment, F* comprises C₆₀. In another embodiment, F* comprisesC₇₀. In a further embodiment, F* comprises C₈₄.

In one embodiment, n is 1. In another embodiment, n is 2. In a furtherembodiment, n is 3 or more.

In one embodiment, R¹ is linked to the fullerene by one covalent bond.In another embodiment, R¹ is linked to the fullerene by two covalentbonds.

In one embodiment, R¹ comprises one reactive group (e.g., diazonium). Inanother embodiment, R¹ comprises two or more reactive groups.

In one embodiment, the diazonium group is represented by

When the counterion is Cl⁻, the diazonium group can be represented by

In one embodiment, the conjugated linker of R¹ comprises alternatingsingle and multiple bonds. In another embodiment, the conjugated linkerof R¹ comprises a conjugated hydrocarbon chain. In a further embodiment,the conjugated linker of R¹ comprises a conjugated hydrocarbon chainsubstituted with one or more heteroatoms (e.g., O, S and N).

In one embodiment, the conjugated linker of R¹ comprises at least onedouble bond or alkenylene bridge. In another embodiment, the conjugatedlinker of R¹ comprises at least one triple bond or alkynylene bridge. Ina further embodiment, the conjugated linker of R¹ comprises at least onearomatic or heteroaromatic ring.

In some embodiments, R¹ is selected from the group consisting of

In some embodiments, R¹ is selected from

In some embodiments, based on the initial weight of the GMA, at least 40wt. %, or at least 60 wt. %, or at least 80 wt. %, or at least 100 wt.%, or at least 120 wt. % of the fullerene compound are incorporated intothe GMA by covalently bonds.

Alternatively, in some embodiments, the fullerene compound isnoncovalently attached to the graphene sheets. In some embodiments, themethod comprises incubating the GMA in a solution comprising at leastone fullerene compound represented by F*—(R²)_(n), wherein: F* comprisesa fullerene having a surface comprising six-membered and five-memberedrings, R² comprises an aromatic or heteroaromatic group (e.g.,phenylamine) and a conjugated linker covalently connecting the aromaticor heteroaromatic group to the fullerene, and n is at least one. In someembodiment, the aromatic or heteroaromatic group comprises 2, 3, 4 ormore fused aromatic or heteroaromatic rings.

In some embodiments, the method comprises incubating the GMA in asolution comprising at least one phenylamine functionlized fullerene. Insome embodiments, the phenylamine functionlized fullerene is representedby

F*—(R²)_(n), wherein: F* comprises a fullerene having a surfacecomprising six-membered and five-membered rings, R² comprises aphenylamine group and a conjugated linker covalently connecting thephenylamine group to the fullerene, and n is at least one.

In one embodiment, n is 1. In another embodiment, n is 2. In a furtherembodiment, n is 3 or more.

In one embodiment, R² is linked to the fullerene by one covalent bond.In another embodiment, R² is linked to the fullerene by two covalentbonds.

In one embodiment, R² comprises one aromatic or heteroaromatic group(e.g., phenylamine). In another embodiment, R² comprises two or morearomatic or heteroaromatic groups.

In one embodiment, the phenylamine group is represented by

In one embodiment, the conjugated linker of R² comprises alternatingsingle and multiple bonds. In another embodiment, the conjugated linkerof R² comprises a conjugated hydrocarbon chain. In a further embodiment,the conjugated linker of R² comprises a conjugated hydrocarbon chainsubstituted with one or more heteroatoms (e.g., O, S and N).

In one embodiment, the conjugated linker of R² comprises at least onedouble bond or alkenylene bridge. In another embodiment, the conjugatedlinker of R² comprises at least one triple bond or alkynylene bridge. Ina further embodiment, the conjugated linker of R² comprises at least onearomatic or heteroaromatic ring.

In some embodiments, R² is selected from the group consisting of

In some embodiments, R² is selected from

In some embodiments, based on the initial weight of the GMA, at least 20wt. %, or at least 40 wt. %, or at least 60 wt. %, or at least 80 wt. %,of the fullerene compound are incorporated into the GMA by noncovalentlyattachment (e.g., physisorption).

In some embodiment, the GMA is a graphene aerogel described in US PatentPublication No. 2012/0034442, which is incorporated by reference in itsentirety. In some embodiment, the GMA is a high-density graphenemonolith described in US Patent Publication No. 2014/0178289, which isincorporated by reference in its entirety. In some embodiment, the GMAis a highly crystalline grapehen aerogel described in U.S. patentapplication Ser. No. 14/820411, which is incorporated by reference inits entirety.

The GMA can comprise, for example, a three-dimensional structure ofgraphene sheets interconnected or crosslinked by chemical bonds such ascovalent carbon-carbon bonds. In some embodiments, 50% or more, or 70%or more, or 80% or more, or 90% or more of the covalent bondsinterconnecting the graphene sheets are sp² carbon-carbon bonds. In someembodiments, 10% or less, or 5% or less, or 3% or less, or 1% or less ofthe graphene sheets are interconnected only by physical crosslinks. Insome embodiments, 10% or less, or 5% or less, or 3% or less, or 1% orless of the graphene sheets are interconnected only by metal crosslinks.

The GMA can be, for example, substantial free of graphene sheets withhydroxyl or epoxide functionalities. In some embodiments, 3% or less, or1% or less, or 0.5% or less, or 0.1% or less of the carbon atoms in theGMA are connected to a hydroxyl or epoxide functionality. In someembodiments, the atomic oxygen content in the GMA is 10% or less, or 5%or less, or 3% or less, or 1% or less.

In some embodiments, the GMA consists essentially of covalentlyinterconnected graphene sheets. In some embodiments, the GMA is not amacroporous foam. In some embodiments, the GMA is substantially free ofa polymer coated on the internal surfaces of the GMA. In someembodiments, the GMA is substantially free of a metal or a metalcompound coated on the internal surfaces of the GMA. In someembodiments, the GMA is substantially free of carbon nanoparticles.

GMA-Fullerene Composite

Many embodiments of the invention relate to a GMA-fullerene compositeproduced by the method described herein.

The weight of the fullerene component compared to the weight of the GMAcomponent can be, for example, at least 20 wt. %, or at least 40 wt. %,or at least 60 wt. %, or at least 80 wt. %, or at least 100 wt. %, or atleast 120 wt. %.

The GMA-fullerene composite can be a monolith having a thickness of, forexample, at least 100 μm, or at least 1 mm, or at least 10 mm, or atleast 100 mm, or about 10 μm to about 1 mm, or about 1 mm to about 100mm.

The GMA-fullerene composite can have an electrical conductivity of, forexample, at least 10 S/m, or at least 20 S/m, or at least 50 S/m, or atleast 100 S/m, or at least 200 S/m, or at least 500 S/m, or about10-1,000 S/m, or about 20-500 S/m, or about 50-200 S/m.

In some embodiments, the GMA-fullerene composite can have a BET surfacearea of, for example, at least 100 m²/g, or at least 200 m²/g, or atleast 300 m²/g, or at least 500 m²/g, or at least 700 m²/g, or about100-1,500 m²/g, or about 200-1,000 m²/g.

In some embodiments, the GMA-fullerene composite can have a Young'smodulus of, for example, at least 10 MPa, or at least 20 MPa, or least50 Mpa, or at least 100 MPa, or at least 200 MPa, or at least 500 MPa,or about 10-1,000 MPa, or about 20-500 MPa.

In some embodiments, the GMA-fullerene composite can have a mesoporevolume of, for example, at least 0.2 cm³/g, or at least 0.5 cm³/g, or atleast 0.8 cm³/g, or at least 1 cm³/g, or at least 1.2 cm³/g, or at least1.5 cm³/g, or about 0.2-5 cm³/g, or about 0.5-3 cm³/g.

In some embodiments, the GMA-fullerene composite comprises at least onefullerene compound covalently connected to at least one graphene sheetvia at least one conjugated linker. In one embodiment, the conjugatedlinker comprises alternating single and multiple bonds. In anotherembodiment, the conjugated linker comprises a conjugated C₁-C₃₀, C₁-C₂₀,C₁-C₁₅, or C₁-C₁₀ hydrocarbon chain. In a further embodiment, theconjugated linker comprises a conjugated C₁-C₃₀, C₁-C₂₀, C₁-C₁₅, orC₁-C₁₀ hydrocarbon chain substituted with one or more heteroatoms (e.g.,O, S and N). In one embodiment, the hydrocarbon chain comprises at leastone double bond or alkenylene bridge. In another embodiment, thehydrocarbon chain comprises at least one triple bond or alkynylenebridge. In a further embodiment, the hydrocarbon chain comprises atleast one aromatic or heteroaromatic ring.

Electrode and Supercapacitor

The GMA-fullerene composite described herein can be used in a variety ofapplications, including supercapacitors, battery electrodes, electricalenergy storage, micro-batteries, hybrid capacitors, next-generationbatteries, hybrid vehicles, and alternative energy storage.

The GMA-fullerene composite described herein is functionallyadvantageous in energy storage applications. In particular, C₆₀ canstore up to 6 electrons, or 1 e⁻/10 carbon atoms (Echegoyen et al., Acc.Chem. Res., 1998, 31, 593-601), compared with 1 e⁻/100 carbon atoms forgraphitic carbon materials (Berger et al., J. Phys. Chem. B, 2004,108(52):19912-19916; Sarma et al., Rev. Mod. Phys., 2011, 83(2):407-470;Wood et al., J. Phys. Chem. C, 2014, 118(1):4-15), a 10-fold increase inelectrical storage capacity. In principle a graphene aerogelfunctionalized with 50 wt % loading of fullerene could achieve 4×greater energy storage compared with an unfunctionalized grapheneaerogel. The measured capacity of an unfunctionalized graphene aerogelelectrode is ˜60 coulombs per gram (C/g) (Campbell et al., J. Mater.Chem. A, 2014, 2:17764-17770). With fullerene functionalization (e.g.,˜50 wt % loading), an electron storage capacity of at least about 100C/g, or at least about 150 C/g, or at least about 200 C/g, or at leastabout 250 C/g, or at least about 300 C/g, or at least about 350 C/g, orat least about 400 C/g, or about 100-500 C/g, or about 200-400 C/g, canbe achieved. With higher fullerene loading (e.g., through the use ofdifferent length linkers), an electron storage capacity of up to about600 C/g, or up to about 550 C/g, or up to about 500 C/g, or about200-600 C/g, or about 300-500 C/g, or about 400-600 C/g, can beachieved. The theoretical maximum electron storage capacity for C₆₀ is803 C/g—the equivalent of 222.5 mAh/g, which is approaching the capacityof lithium ion battery cathode materials (e.g., LiCoO₂ theoretical maxis 274 mAh/g).

Accordingly, many embodiments of the invention described herein alsorelate to an electrode comprising the GMA-fullerene composite, as wellas a supercapacitor comprising the electrode.

In one embodiment, the supercapacitor further comprises an organicliquid electrolyte in contact with the electrode. In another embodiment,the supercapacitor further comprises an ionic liquid electrolyte withthe electrode. In an additional embodiment, the supercapacitor furthercomprises an aqueous electrolyte with the electrode.

Unlike anthraquinone and other redox-based charge-storage strategiesthat involve chemical reactions (proton-coupled electron transfer),fullerenes store charge in a purely electric double-layer capacitance(EDLC) mechanism that is an interfacial phenomenon and does not involvea chemical reaction, which means that charge/discharge rates can befaster and long-term stability will increase. Moreover, because thepurely EDLC mechanism does not require protons, the GMA-fullerenecomposite described herein can be used in supercapacitors in combinationwith organic or ionic liquid electrolytes, which greatly increases theoperational voltage window and thus the total energy stored (E=½ CV²).

WORKING EXAMPLES Example 1 Synthesis of GMA

Graphene macro-assemblies (GMA) were prepared in a similar manner towhat were previously reported in Worsley et al., Chem. Commun.,48:8428-8430 (2012), which is incorporated herein by reference. Grapheneoxide (GO, 1-2 layer, 300-800 nm diameter sheets) was purchased fromCheaptubes and used as received. GO was dispersed in Milli-Q H₂O (20mg/mL) by ultrasonication for 24 h, and ammonium hydroxide catalyst (211μL/g) was added to the resulting suspension. The GO suspension/catalystmixture was cast into disk shaped molds, sealed, and placed in a 75° C.oven for 72 h for crosslinking/gelation. The monolithic disks werewashed in water, followed by acetone, and dried with supercritical CO₂.The disks were then carbonized at 1050° C. for 3 h under flowing N₂ toremove oxygen functionality (final O content<2 at. %). The resulting GMAdisks are approximately 1 cm in diameter by 250 μm thickness, weigh ˜1mg, have density of ˜0.07 g/cm³, and have a BET surface area of ˜1300m²/g.

Example 2 Synthesis of 1-(4-aminophenyl)ethano-p-toluenesulfonylhydrazone

A mixture of 1-(4-aminophenyl)ethano (1.0 g, 3.36 mmol) andp-toluenesulfonyl hydrazone (2.2 g, 11.88 mmol) in MeOH (20 mL) wasstirred and refluxed for 2 days. The mixture was left without heatingfor 1 day and then cooled to −10° C. The white powder was then filteredand washed with cold MeOH and dichloromethane, and dried under vacuum(65% yield).

Example 3 Synthesis of 1-(4-aminophenyl)ethano-C₆₀ (PA-C₆₀)

Diazo addend was prepared in-situ by dissolving1-(4-aminophenyl)ethano-p-toluenesulfonyl hydrazone (122.7 mg, 0.208mmol) in 1.2 mL of anhydrous pyridine under N₂ atmosphere. NaOMe (56.3mg, 1.042 mmol) was added, and the mixture was stirred for 30 min. Asolution of 75.0 mg of C₆₀ (0.1042 mmol) in 7 mL of o-DCB (aka,1,2-dichlorobenzene) was added and stirred at 110 C for 6 h. The solventfrom the reaction mixture was removed under nitrogen and the crudeproduct was purified by silica gel column using initially CS₂ as theeluent to collect the unreacted [60]fullerene, followed by CS₂:CH₂Cl₂1:1 to collect the monoadduct (41%).

Example 4 Synthesis of 1-(4-diazoniumphenyl)ethano-C60 tetrafluoroborate

Diazonium salt was prepared by dissolving 1-(4-aminophenyl)ethano-C₆₀ ina 5:1 mixture of CH₃CN:CH₂Cl₂ under N₂ atmosphere, the solution was colddown to −30 C and nitrosonium tetrafluoroborate (NOBF₄) was added. Themixture was stirred for 1.5 h. The solvent from the reaction mixture wasremoved under reduced pressure and the crude product was purified bywashing the crude mixture with CS₂:CH₂Cl₂ 7:3 to remove the unreactedmonoadduct and THF to remove the excess of diazonium salt.

Example 5 Noncovalent Functionalize of GMA with C₆₀

GMA was non-covalently functionalized with C₆₀ via physisorption. Thefollowing loading percentages based on the initial weight of the GMAwere achieved.

4.5 mM C₆₀ in CS₂, 3 days=16% loading

4 mM C₆₀ in CS₂, 15 h=13% loading

2 mM C₆₀ in CS₂, 15 h=5% loading

FIG. 1(A) shows a GMA-C₆₀ composite obtained by noncovalentlyfunctionalizing the GMA with 4.5 mM C₆₀, and FIG. 1(B) shows CV of aGMA-C₆₀ composite with 13% loading of C₆₀ in MeCN/TBAP electrolyte (5mV/s).

Example 6 Noncovalent Functionalize of GMA with PA-C₆₀

GMA was non-covalently functionalized with PA-C₆₀ via physisorption.PA-C₆₀ is more soluble than unmodified C₆₀. The following loadingpercentages based on the initial weight of the GMA were achieved.

7 mM PA-C₆₀ in CS₂:CH₂Cl₂ 7:3, 3 days=87% loading

6 mM PA-C₆₀ in CS₂:CH₂Cl₂ 7:3, 17 h=50% loading

4 mM PA-C₆₀ in CS₂:CH₂Cl₂ 7:3, 14 h =26% loading

2.1 mM PA-C₆₀ in CS₂:CH₂Cl₂ 7:3, 14 h =16% loading

FIG. 2(A) shows a GMA-PA-C₆₀ composite obtained by noncovalentlyfunctionalizing the GMA with 7 mM PA-C₆₀, and FIG. 2(B) shows CV of aGMA-PA-C₆₀ composite with 50% loading of PA-C₆₀ in MeCN/TBAP electrolyte(5 mV/s).

Example 7 Covalent Functionalization of GMA with Diazonium-C₆₀

GMA was added to a 1 mM solution of diazonium-C₆₀ in THF, and heat at60° C. for 2 days. A final loading of 67% based on the initial weight ofthe GMA was achieved.

Example 8 In-situ Synthesis of Diazonium-C₆₀ and CovalentFunctionalization of GMA

To a 4 mM solution of PA-C₆₀ in o-DCB:MeCN 4:1, 2 drops of isopentylnitrite were added and a precipitate was observed immediately. GMA wasthen added and heated at 85° C. over the weekend. After the weekend theprecipitate and solution were removed and GMA was washed several timeswith CS₂, CH₂Cl₂ and THF to remove not chemically bonded fullerene. GMAwas then left in THF overnight and dried in the oven at 80° C. for 2days. A final loading of 138% based on the initial weight of the GMA wasachieved.

FIG. 4 shows CV of a GMA-fullerene composite with 138% loading ofdiazonium-C₆₀ in MeCN/TBAP electrolyte (10 mV/s), which is evidentlyfunctionally superior compared to CV of a non-functionalized GMA inMeCN/TBAP electrolyte (5 mV/s) as shown in FIG. 3.

EXAMPLE 9 Noncovalent Functionalize of GMA with C₆₀

GMA was non-covalently functionalized with C₆₀ via physisorption. Thefollowing loading percentages based on the initial weight of the GMAwere achieved.

2-6 mM C₆₀ in CS₂, 15 h=15%±4 loading

FIG. 7 shows CV in MeCN/TBAP electrolyte of a GMA-C₆₀ with 17 wt. %loading of C₆₀ (5 mV/s, cycle 1, black line) and non-functionalized GMA(5 mV/s, cycle 1, red line).

EXAMPLE 10 Noncovalent Functionalize of GMA with C₆₀-1

GMA was non-covalently functionalized with C₆₀-1 via physisorption.C₆₀-1 is more soluble than unmodified C₆₀. The following loadingpercentages based on the initial weight of the GMA were achieved.

2-6 mM C₆₀-1 in CS₂, 15 h=43±3% loading

FIG. 8 shows CV in MeCN/TBAP electrolyte of a GMA-C₆₀-1 composite with44 wt. % loading of C₆₀-1 (5 mV/s, cycle 1, black line) andnon-functionalized GMA (5 mV/s, cycle 1, red line).

EXAMPLE 11 In-situ Synthesis of Diazonium-C₆₀ and CovalentFunctionalization of GMA

To a 4 mM solution of C₆₀-1 in o-DCB:MeCN 4:1, 2 drops of isopentylnitrite were added and a precipitate was observed immediately. GMA wasthen added and heated at 85° C. over the weekend. After the weekend theprecipitate and solution were removed and GMA was washed several timeswith CS₂, CH₂Cl₂ and THF to remove not chemically bonded fullerene. GMAwas then left in THF overnight and dried in the oven at 80° C. for 2days. A final loading of 138% based on the initial weight of the GMA wasachieved.

FIG. 9 shows CV in MeCN/TBAP electrolyte of a covalently functionalizedGMA-fullerene composite with diazonium-C₆₀, final loading 138 wt. % (5mV/s, black line) and non-functionalized GMA (5 mV/s, cycle 1, redline).

As used herein, the singular terms “a,” “an,” and “the” include pluralreferents unless the context clearly dictates otherwise. Thus, forexample, reference to a compound can include multiple compounds unlessthe context clearly dictates otherwise.

As used herein, the terms “substantially,” “substantial,” and “about”are used to describe and account for small variations. When used inconjunction with an event or circumstance, the terms can refer toinstances in which the event or circumstance occurs precisely as well asinstances in which the event or circumstance occurs to a closeapproximation. For example, the terms can refer to less than or equal to±10%, such as less than or equal to ±5%, less than or equal to ±4%, lessthan or equal to ±3%, less than or equal to ±2%, less than or equal to±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or lessthan or equal to ±0.05%.

Additionally, amounts, ratios, and other numerical values are sometimespresented herein in a range format. It is to be understood that suchrange format is used for convenience and brevity and should beunderstood flexibly to include numerical values explicitly specified aslimits of a range, but also to include all individual numerical valuesor sub-ranges encompassed within that range as if each numerical valueand sub-range is explicitly specified. For example, a ratio in the rangeof about 1 to about 200 should be understood to include the explicitlyrecited limits of about 1 and about 200, but also to include individualratios such as about 2, about 3, and about 4, and sub-ranges such asabout 10 to about 50, about 20 to about 100, and so forth.

In the foregoing description, it will be readily apparent to one skilledin the art that varying substitutions and modifications may be made tothe invention disclosed herein without departing from the scope andspirit of the invention. The invention illustratively described hereinsuitably may be practiced in the absence of any element or elements,limitation or limitations, which is not specifically disclosed herein.The terms and expressions which have been employed are used as terms ofdescription and not of limitation, and there is no intention that in theuse of such terms and expressions of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognizedthat various modifications are possible within the scope of theinvention. Thus, it should be understood that although the presentinvention has been illustrated by specific embodiments and optionalfeatures, modification and/or variation of the concepts herein disclosedmay be resorted to by those skilled in the art, and that suchmodifications and variations are considered to be within the scopes ofthis invention.

What is claimed is:
 1. A composition comprising a graphenemacro-assembly (GMA)-fullerene composite, wherein the GMA-fullerenecomposite comprises a GMA comprising a three-dimensional network ofgraphene sheets crosslinked by covalent carbon bonds, and at least 20wt. % of at least one fullerene compound incorporated into the GMA basedon the weight of the GMA.
 2. The composition of claim 1, wherein thefullerene compound is covalently bound to the graphene sheets.
 3. Thecomposition of claim 2, wherein the fullerene compound is representedby: F*—(R¹)_(n), wherein: F* comprises a fullerene having a surfacecomprising six-membered and five-membered rings, R¹ comprises aconjugated linker covalently linking the fullerene to the graphenesheet, and n is at least one.
 4. The composition of claim 4, wherein theconjugated linker comprises a conjugated C₁-C₃₀ hydrocarbon chainoptionally substituted with one or more heteroatoms.
 5. The compositionof claim 4, wherein the conjugated linker comprises alternating singleand multiple bonds, and optionally comprises at least one aromatic orheteroaromatic ring.
 6. The composition of claim 4, wherein n is 1 or 2,F* is C₆₀ or C₇₀, and R¹ is


7. The composition of claim 1, wherein the fullerene compound isnoncovalently attached to the graphene sheets.
 8. The composition ofclaim 7, wherein the fullerene compound comprises at least onephenylamine functionlized fullerene.
 9. The composition of claim 8,wherein the phenylamine functionlized fullerene is represented by:F*—(R²)_(n), wherein: F* comprises a fullerene having a surfacecomprising six-membered and five-membered rings, R² comprises aphenylamine group and a conjugated linker covalently connecting thephenylamine group to the fullerene, and n is at least one.
 10. Thecomposition of claim 9, wherein the conjugated linker comprises aconjugated C₁-C₃₀ hydrocarbon chain optionally substituted with one ormore heteroatoms.
 11. The composition of claim 9, wherein the conjugatedlinker comprises alternating single and multiple bonds, and optionallycomprises at least one aromatic or heteroaromatic ring.
 12. Thecomposition of claim 9, wherein n is 1 or 2, F* is C₆₀ or C₇₀, and R² is


13. The composition of claim 1, wherein the GMA-fullerene compositecomprises at least 50 wt.% of the fullerene compound based on the weightof the GMA.
 14. The composition of claim 1, wherein the GMA-fullerenecomposite comprises at least 100 wt. % of the fullerene compound basedon the weight of the GMA.
 15. The composition of claim 1, wherein theGMA-fullerene composite is a monolith having a thickness of at least 1mm.
 16. The composition of claim 1, wherein the GMA-fullerene compositehas an electrical conductivity of at least 10 S/m.
 17. The compositionof claim 1, wherein the GMA-fullerene composite has a mesopore volume ofat least 0.5 cm³/g.
 18. The composition of claim 1, wherein theGMA-fullerene composite has a BET surface area of at least 200 m²/g. 19.The composition of claim 1, wherein the GMA-fullerene composite has aYoung's modulus of at least 20 MPa.
 20. A supercapacitor comprising anelectrode comprising the GMA-fullerene composite of claim 1, and furthercomprising an organic or ionic liquid electrolyte in contact with theelectrode.